Burn a Lot of Calories in a Short Amount of Time
You can burn calories quickly using HIIT.
One study compared the calories burned during 30 minutes each of HIIT, weight training, running and biking.
The researchers found that HIIT burned 25–30% more calories than the other forms of exercise.
In this study, a HIIT repetition consisted of 20 seconds of maximal effort, followed by 40 seconds of rest.
This means that the participants were actually only exercising for 1/3 of the time that the running and biking groups were.
Although each workout session was 30 minutes long in this study, it is common for HIIT workouts to be much shorter than traditional exercise sessions.
This is because HIIT allows you to burn about the same amount of calories, but spend less time exercising.
It Can Help you Lose Fat
Studies have shown that HIIT can help you lose fat - One review looked at 13 experiments and 424 overweight and obese adults.
Interestingly, it found that both HIIT and traditional moderate-intensity exercise can reduce body fat and waist circumference.
Additionally, one study found that people performing HIIT three times per week for 20 minutes per session lost 4.4 pounds, or 2 kgs, of body fat in 12 weeks — without any dietary changes.
Perhaps more important was the 17% reduction in visceral fat, or the disease-promoting fat surrounding your internal organs.
Reduce Heart Rate and Blood Pressure
HIIT may have important health benefits, as well.
A large amount of research indicates that it can reduce heart rate and blood pressure in overweight and obese individuals, who often have high blood pressure.
One study found that eight weeks of HIIT on a stationary bike decreased blood pressure as much as traditional continuous endurance training in adults with high blood pressure.
In this study, the endurance training group exercised four days per week for 30 minutes per day, but the HIIT group only exercised three times per week for 20 minutes per day.
Some researchers have found that HIIT may even reduce blood pressure more than the frequently recommended moderate-intensity exercise.
Keep in mind, it appears that high-intensity exercise does not typically change blood pressure in normal-weight individuals with normal blood pressure.
High-intensity interval training is a very efficient way to exercise, and may help you burn more calories than you would with other forms of exercise.
Some of the calories burned from high-intensity intervals come from a higher metabolism, which lasts for hours after exercise.
Overall, HIIT produces many of the same health benefits as other forms of exercise in a shorter amount of time.
These benefits include lower body fat, heart rate and blood pressure. HIIT may also help lower blood sugar and improve insulin sensitivity.
So, if you are short on time and want to get active, consider trying high-intensity interval training.
Written by Grant Tinsley, PhD on June 2, 2017
Increase Your Metabolic Rate for Hours After Exercise
One of the ways HIIT helps you burn calories actually comes after you are done exercising.
Several studies have demonstrated HIIT's impressive ability to increase your metabolic rate for hours after exercise.
Some researchers have even found that HIIT increases your metabolism after exercise more so than jogging and weight training.
In the same study, HIIT was also found to shift the body's metabolism toward using fat for energy rather than carbs.
Another study showed that just two minutes of HIIT in the form of sprints increased metabolism over 24 hours as much as 30 minutes of running
Improve Oxygen Consumption
Oxygen consumption refers to your muscles' ability to use oxygen, and endurance training
is typically used to improve your oxygen consumption.
Traditionally, this consists of long sessions of continuous running or cycling at a steady rate.
However, it appears that HIIT can produce the same benefits in a shorter amount of time
One study found that five weeks of HIIT workouts performed four days per week for 20 minutes each session improved oxygen consumption by 9%
This was almost identical to the improvement in oxygen consumption in the other group in the study, who cycled continuously for 40 minutes per day, four days per week.
Another study found that eight weeks of exercising on the stationary bike using traditional exercise or HIIT increased oxygen consumption by about 25%.
Once again, the total time exercising was much different between groups: 120 minutes per week for the traditional exercise versus only 60 minutes per week of HIIT.
Gain Muscle with High Intensity
In addition to helping with fat loss, HIIT could help increase muscle mass in certain individuals.
However, the gain in muscle mass is primarily in the muscles being used the most, often the trunk and legs.
Additionally, it's important to note that increases in muscle mass are more likely to occur in individuals who were less active to begin with.
Some research in active individuals has failed to show higher muscle mass after HIIT programs.
Weight training continues to be the "gold standard" form of exercise to increase muscle mass, but high-intensity intervals could support a small amount of muscle growth.